Caption: Especially interesting moons of the Solar System shown to-scale with the Earth shown to-scale for comparison.

These moons have been selected for large size or some other special feature of interest.

Features:

1. The displayed moons plus a few others (in order of increasing mean orbital radius) for each parent planet or other Solar System object are given below with mean diameter in some cases (in brackets) and moon-size order for the largest ones (in brackets):
   1. Earth: Moon (3474, 5th).
   2. Mars (see Martian moons): Martian moons Phobos (22.2 km), Deimos (12.4 km). The Martian moons were discovered by Asaph Hall (1829--1907) in 1877. The tidal force is causing Phobos to inspiral to its eventual doom and Deimos to outspiral (see Wikipedia: Martian Moons: Characteristics).
   3. 243 Ida (an asteroid asteroid belt): Dactyl (about 1.5 km).
   4. Jupiter (see Jovian moons, Galilean moons): Io (3643, 4th), Europa (3122 km, 6th), Ganymede (5268 km, 1st), Callisto (4821 km, 3rd).
   5. Saturn: (see Saturnian moons): Mimas, Enceladus, Tethys, Dione, Rhea (1528, 9th), Titan (5152 km, 2nd), Hyperion, Iapetus (1469, 11th), Phoebe.
   6. Uranus (see Uranian moons): Puck, Miranda, Ariel, Umbriel, Titania (1577 km, 8th), Oberon (1523 km, 10th).
   7. Neptune (see Neptunian moons): Proteus, Triton (2707 km, 7th), Nereid.
   8. Pluto (ex-planet, dwarf planet, see Plutonian moons): Charon (1207 km, 12th).
   9. Eris (dwarf planet): Dysnomia (of order 300 km).

2. The largest Solar-System moons in order of decreasing diameter are:
   Ganymede (5268 km, 1st), Titan (5152 km, 2nd), Callisto (4821 km, 3rd), Io (3643, 4th), Moon (3474, 5th), Europa (3122 km, 6th), Triton (2707 km, 7th), Titania (1577 km, 8th), Rhea (1528, 9th), Oberon (1523 km, 10th), Iapetus (1469, 11th), Charon (1207 km, 12th).

   Note, only the Moon (5th largest) and Titan (2nd largest) break up the dominance in size of the Galilean moons.

3. Some folks think that largest moons are really just small planets that orbit other planets.

4. The moons of minor planet (astro-bodies too small to be planets) are called minor-planet moons and just minor planet themselves.

5. Very small moons have been called, unofficially, moonlets.

6. There are NO known moons of moons in the Solar System, but some tiny ones may exist.

   Moons of moons of certainly exist in some other planetary systems.

7. Moons in other planetary systems are called exomoons when there is some need to distinguish them from Solar-System moons.

   No exomoons has been discovered yet, but some probably will be in the near future.

8. See also Wikipedia: Natural Satellites and Wikipedia: List of the natural satellites.